1. Field of the Invention
The present invention relates to a display apparatus used for a computer terminal monitor, a camera view finder, a television receiver, a projector, etc. Particularly, the present invention relates to a display apparatus capable of controlling power supplied from a power source on the basis of a plurality types of signals.
2. Related Background Art
Since there are demands for energy saving of office automation apparatus such as computers, terminal monitors thereof, etc., regulations on energy saving are established by some institutions. In accordance with the regulations on an energy-saving monitor, the energy-saving monitor must be set so that the power consumption of the monitor is decreased to 30 W or less a predetermined time after the operator of a computer stops using a keyboard.
Examples of conceivable means for satisfying the regulation item are the following means:
1. A computer device for supplying image signals is partially changed so as to superimpose, on a monitor synchronous signal, the information that a predetermined time has passed after the operator stops using the keyboard. The monitor decodes the information, and controls the power consumption of the monitor to force it to decrease on the basis of the information. PA0 2. A computer device for supplying image signals is partially changed so as to change image data into predetermined data and output the data to the monitor side after the passage of a predetermined time after the operator stops using the keyboard. The monitor discriminates the image data, and, when predetermined image data is continuously sent for a predetermined time, controls the power consumption of the monitor itself to force it to decrease. PA0 3. The monitor makes a decision as to whether or not the image data sent from a computer device for supplying image signals is changed, and, when the image data is not changed for a predetermined time, controls the power consumption of the monitor itself to force it to decrease.
However, a conventional low-power consumption mode uses only the above methods 1 or 2 for controlling the monitor to bring it into a low-power consumption mode when a computer or television requests the low-power consumption mode, not the above method 3 of transferring to the low-power consumption mode based on a decision by the monitor itself. This means that even when the monitor itself requests to transfer to the low-power consumption mode, it is impossible to transfer to the low-power consumption mode unless a request for the low-power consumption mode is given from the side of a computer or television. It is thus impossible to realize the function to transfer to the low-power consumption mode in as short of intervals as possible for increasing the life of a back light in the monitor.
In a monitor having a memory function, e.g., a ferroelectric liquid crystal panel display monitor, a plasma display monitor or the like, when input image data is not changed, display data does not disappear even if electric power supplied to the monitor is partially or completely decreased. If the image data is not changed, it is thus possible to realize the low-power consumption mode by cutting off the power supplied to the monitor. However, it was found to be necessary for improving the effect that not only a request from a computer or the like can be waited for, but also the normal mode can be transferred to the low-power consumption mode on the side of the monitor itself, as in method 3.
Although, in methods 1 and 2, a new function must be added to a computer or television system, even if the low-power consumption mode function is provided on the monitor side in an old type computer or television system, the system cannot comply with the function.
Method 3 produces the problem to be solved that when a cursor flickers or a time is displayed, even if the user does not push the keyboard, image data is always changed, thereby making it impossible to transfer to the low-power consumption mode.